This project is concerned with (a) the genetic diversity of Trypanosoma cruzi and its implications to the epidemiology, course and diagnosis of Chagas' disease, (b) the development of high resolution flow cytometry instrumentation for analyses of cell populations and, (c) the utilization of flow cytometry and low light level video microscopy for the analyses of infectious agents. The marked differences in total DNA/cell between T cruzi stocks discovered by flow cytometry has been confirmed using conventional diphenylamine analysis. Electron beam x-ray microchemical analyses of the epimastigote stage of T. cruzi clones demonstrate marked interclonal differences in Fe, Zn, S, Mg, K, Ca and P. Spectroscopic analyses reveal that T. cruzi clones with high Fe content also have a proportionately higher cytochrome content that T. cruzi clones with low Fe content. Studies of inter-clonal heterogeneity are being extended to Leishmania spp.